Recap

• A remote is repository hosted elsewhere than your local machine (e.g., on GitHub)
  • The remote is named origin or upstream.
  • On GitHub a remote URL looks like
    • https://github.com/OWNER/REPO.git or
    • git@github.com:OWNER/REPO.git

Recap

Recap

Recap

• A fork is a copy of a repository on a remote server (e.g., GitHub)
• A clone is a copy of a repository on your local machine

No GitHub

Yours

Yours - setup

• If the local repo exists first:
  • For detailed instructions see Existing project, GitHub last.
  • usethis::use_github().
  • Command line/RStudio: Task can’t be completed fully (see Chapter 25.2)
• If the remote repo exists first:
  • For detailed instructions see New RStudio Project via git clone.
  • usethis::create_from_github("OWNER/REPO", fork = FALSE).
  • Command line: git clone <URL>
  • RStudio: File > New Project > Version Control > Git

Ours

Theirs

Fork (of theirs)

Fork (of theirs) - setup

• Detailed instructions are given in Fork and clone.
• usethis::create_from_github("OWNER/REPO", fork = TRUE).
• Command line Git or RStudio: You can’t complete this task fully

Fork (of ours)

Fork (salvageable)

Recap

• A commit is a snapshot of your project at a particular point in time.
  • It captures changes made to files and records them in the version history.
  • git commit
• Amend is used to rewrite the last commit (e.g., update commit message or files).
  • git commit --amend
  • Allows fixing minor issues without creating a new commit

Mountain Climbing Analogy

Mountain Climbing Analogy

Mountain Climbing Analogy

Mountain Climbing Analogy

When to Use Amend

• If you made a minor error or forgot to add files
• If you need to update the commit message
  • git commit --amend
  • RStudio makes it very easy

Potential Pitfalls

• Amending after pushing:
  • You should avoid amending commits that have already been pushed to a shared repo
  • Amending pushed commits rewrites history and can cause problems for collaborators
  • Use with caution when working on shared repositories

Workflow - Step 1

Start with your project in a functional state. - Use git status to check this.

Workflow - Step 2

::: aside Initial status of project. :::

Workflow - Step 2

** Don’t push!**

Workflow

2. Get to work

• Do a bit more work.
• Re-check that your project is still in a functional state.
• Stage and commit again, but this time amend your previous commit.
  • git commit --amend --no-edit

** Don’t push!**

Workflow

2. Get to work

• Keep going until you’ve achieved your final objective.
• Now ammending the commit, but add a real message
  • git commit --amend -m "Implement awesome feature"
• Push the changes: git push

Workflow

3. What if I need to fall back?

• Imagine you’re in the middle of a Repeated Amend workflow and you make some changes that break your project:

A -- B -- C -- WIP* 

• You want to fall back to the last good state, represented by WIP*.
  • This is called a hard reset to the WIP* state.
  • Meaning: “reset my files to their state at the most recent commit”.
• How to achieve?
  • command line: git reset --hard
  • RStudio:
    • Click on “Diff” or “Commit”.
    • Select a file with changes you do not want.
    • Use “Discard All” to discard all changes in that file.
    • Use “Discard chunk” to discard specific changes in a file.

Workflow

4. What if I did push?

Let’s imagine you pushed this state to GitHub by mistake:

A -- B -- C -- WIP (85bf30a)

and proceeded to git commit --amend again locally, leading to this state:

A -- B -- C -- WIP* (6e884e6)

Workflow

4. What if I did push?

You have two choices:

1. You’re working with collaborators:

• Save a copy of any files that exist locally (with changes) to a new file path, temporarily.
• Hard reset your local repo to C (git reset –hard HEAD^) and pull from GitHub.

A -- B -- C -- WIP (85bf30a)

• Bring any files saved temporarily elsewhere back into the repo now; save, stage, commit, and push.

A -- B -- C -- WIP (85bf30a) -- E

Workflow

4. What if I did push?

You have two choices:

2. You have no collaborators:

• Make sure your local commit has a real, non-“WIP” message.
• Force push your history to GitHub (git push --force).

A -- B -- C -- D